For dispatch purposes, newspapers and magazines are usually stacked, the stacks being strapped at least once with a strap or band and they may be enveloped or wrapped with a film or foil prior to strapping. Stacks packed in this way are stable and easy to handle as a result of the strapping and, due to the film wrapping, at least the outermost products are protected against environmental influences such as moisture or dirt and also against mechanical damage. Depending on the stack stability and on the size of the stacked articles, single or multiple strapping is used, the multiple strapping consisting of at least two parallel straps or of at least two straps at right angles to each other.
For wrapping and strapping serially supplied stacks, as well as of other substantially parallelepipedic articles, the most varied methods and apparatus are known and these are, e.g., described in European patent publication numbers EP-0894721, EP-0890509, and EP-0949341. With most of these methods and apparatus, it is possible to produce, with short cycle times, adequately stable stack packs, provided that the heights of all the supplied stacks falls within a predetermined range and in particular provided that none of the stacks has a height smaller than a predetermined minimum height.
The minimum stack height limitation may have various reasons. The stacked products can, e.g., be so bendable or flexible that in a small stack, they are bent by a taut strap so that the strap loosens and the pack becomes unstable. If the strap is welded together on a perpendicular lateral face of the stack, in a small stack, the weld point can be higher than the stack, so that taut strapping cannot be obtained.
For dispatch purposes, predetermined numbers of newspapers and magazines are made ready by stacking and packing and a dispatch unit usually comprises a plurality of standard packs (stacks with a standard height) and, e.g., one top pack (smaller than the standard pack). Such top packs can contain a very small number of magazines or newspapers or even a single magazine or newspaper. Due to the aforementioned limitation to the stack height in the known strapping machines, the top packs may have to be supplied to a separate apparatus, such that not only additional wrapping/strapping apparatus but also additional conveying paths and switch points are required. Because in most cases it is important that standard and top packs are discharged from the packaging process in the same order in which the stacks forming these packs were supplied, the allocation of the stack flow to different packing machines and the bringing together of the packed flow after packing requires complicated automatic control or necessitates manual reorganization.